Method of producing and applying enamel coatings to metallic surfaces



' ess.

UNETE STATES e aser oaaica.

HERBERT M. SMITH, OF GREAT BARRINGTON, MASSACHUSETTS, A SSIGNOR, TO STAN- LEY INSULATING COMPANY, OF GREAT BARRINGTON,

PORATION 0F MAINE.

MASSACHUSETTS, A COR- METHOD OF PRODUCING AND APIE LYING ENAMEL COATINGS TO METALLIC SURFACES.

No Drawing.

To (177 whom it may concern:

Be it known that I, HERBERT MILLS SMITH, a citizen of the United States, residing at Great Barrington, in the county of Berkshire and State of Massachusetts. have invented certain new and useful Improvements in Methods of Producing and Applying Enamel Coatings to Metallic Surfaces,.

of which the following is a specification.

This invention relates to a method of pro.- ducing and applying a vitreous enamel for insulated containers and receptacles and that will stand mechanical shock, rapid thermal changes and deflection. With this object in view I have produced anew combination of materials, have devised a novel Manganese dloxlde and efiective way of preparing the metallic surface to which it is to be applied. and have provided for the removal, as rapidly as they are formed, of the gases which are formed during the fusion of the enamel.

Other objects of the invention, more less broad than those stated above. together with the advantages inherent. will appear from the following description of the elements. combinations, arrangements of parts and applications of principles constituting the invention; and the scope of protection contemplated will appear from the claims.

Assuming that the surface to Wvhich the enamel is to be applied is a metal like steel,

the first step is to heat the receptacle so as to consume and drive 03 any organic or greasy coating which may be on the metal. As the next step I remove the metallic oxides, as by any suitable electrolytic proc- Sincesuch electrolytic process ordinarily involves them se of an acid electrolyte. all trace of acid mustbe removed from the metal. This I accomplish by first washing the surface in water and then in a solution which will neutralize any remaining acid.

The result is that I have a metal with an eggshell matte surface or finish to which the enamel coat will most effectively adhere.

The enamel consists of two distinct combinations of materials. One is called the ground coat and consists of the following Specification of Letters Patent.

Patented Aug. 15, 1922.

Application filed September 30, 1918. Serial No. 256,283.

materials in about the amounts and proportions stated:

Amount. Per cent. Feldspar 36.00lbs. 23. 74 Quartz 33. 00"" 21.76 Borax 50.20 33. 11 Soda nitrate 10.70 7. 04 Saltpeter 6.50 4.28 Clay 6.00 3.95 Fluorspar 6.30 4.15 Epsom salts .19 .13 Cobalt oxide l .25 .18 Nickel oxide .30 .21 Copper oxide .50 .35 Magnesia carbonate 1.20 .80

The above materials are mixed and fused to make a frit, being afterwards ground up and then mixed with a small quantity of water to form a mass of about the consist ency of thick cream.

The cover coat contains the following materials in aboutthe amounts and proportions stated,'and these materials are mixed 7 and fused just as are the materials for the ground coat:

The'receptacle properly cleaned as before described is filled with a quantity of the liquid enamel mixture. the ground coat, and shaken so as to distribute the enamel mixture over the surface. Then the receptacle is emptied and heated so as to dry out the enamel. Next it is put in a furnace heated to about one thousand degrees centigrade and left for approximately three minutes for fusion. While" this fusion is going on a blast of hot air. is introduced into the interior of the receptacle for the purpose of removing as fast as they are formed, .the gases resulting from the fusion of the various materials which would otherwise result in a bubbled and uneven surface. Incidentally the blast may have the effect of evening the distribution of the fused coating. The

receptacle is now removed from the furnace and allowed to cool and then is filled with the second or covering enamel mixture v cooled and the receptacle is again filed with assume the coating mixture and emptied and put into the furnace again as before with the air blast but with a temperature now reduced to about 7 50 C., thus accomplishing the fusion of the third coat without disturbing either of the previous coats.

The result is a vitreous flexible coating evenly distributed and uniform in texture which will stand mechanical shock, rapid thermal changes, and bending or deflection of the walls to which it isapplied.

I claim I 1. As a part of the process of enameling, applying an enamel mixture to a surface which is to be coated thereby, distributing the material over the surface, subjecting it to a fusion temperature and applying an air blastthereto while the fusion is going on.

2. As a part of the process of enameling, applying an enamel mixture to a surface distributing the material over the surface, and subjecting the material to a heated air blast to remove the gases resulting from fusion while the fusion is going on.

,In testimony whereof I afiix my signature in presence of two Witnesses.

HERBERT M. SMITH. 

